While running away from
home for reasons that are eminently defensible, Emilie’s plans to stow
away on the steamship Merry Bell and reach her cousin in the big city go
awry, landing her on the wrong ship and at the beginning of a fantastic
adventure. Taken under the protection of Lady Marlende, Emilie learns
that the crew hopes to use the aether currents and an experimental
engine, and with the assistance of Lord Engal, journey to the interior
of the planet in search of Marlende’s missing father. With the ship
damaged on arrival, they attempt to traverse the strange lands on their
quest. But when evidence points to sabotage and they encounter the
treacherous Lord Ivers, along with the strange race of the sea-lands,
Emilie has to make some challenging decisions and take daring action if
they are ever to reach the surface world again. —from Goodreads.

I've never read a book by Martha Wells before, and generally Journey to the Center of the Earth-type novels aren't my cup of tea, probably because mole-people don't interest me and I have an aversion to the dark. Emilie and the Hollow World sounded just different enough to be intriguing.

That said, after I received the ARC from Angry Robot on NetGalley, it took me forever to start reading, which I regret, because I really liked it! However, I was a bit prejudiced, given the YA marketing & cover design, and I thought, going in, this book was probably going to be quite fluffy. Well, I overestimated the fluff (minimal) and underestimated (or misread) the age of the protagonist, Emilie. I read the first few pages assuming she was a plucky 11 or 12 year old — not so. Emilie is 16, and further, some of the elements of her backstory (and of the beginning of the sequel if there will be one) are more northward in the YA spectrum than an 11 year old character might have. But only slightly. One or two degrees northward. Still appropriate and not at all shocking for any middle-grade fiction reader.
So despite being even older than the intended audience than I'd expected to be, I still enjoyed the story.

Very steampunk, great world-building (in an aquatic way, a personal favorite), and likeable characters, especially Emilie and Miss Marlende. Sort of like the child protégé of Gail Carriger's Alexia Tarabotti, though much less prim and chatty. I also quite liked how Wells describes the non-human characters.

I would recommend this book to middle-grade readers and older who like steampunk, The Swiss Family Robinson (do kids still read that?), Robinson Crusoe, Disney's "Atlantis: The Lost Empire" (this especially! A favorite of mine), and Scott Westerfeld's Leviathan series.

p.s. I went back and read some reviews on The Swiss Family Robinson and I am completely unsurprised to find out how much many adults hate it. I'm glad I read it and saw the movie as a child. I remember really liking it, but given all the criticism about how much senseless animal shooting goes on, maybe it makes sense I grew up to be a vegetarian.